ABSTRACT
<b>Introduction</b> : The purpose of this study was to clarify the antimicrobial susceptibility of <i>Haemophilus influenzae</i> in central Tokyo over a ten-year period.<br><b>Methods</b> : We investigated the susceptibility of <i>Haemophilus influenzae</i> isolated in Tokyo Saiseikai Central Hospital for 10 years from 2004 through 2013.<br><b>Results</b> : Significant increases in the proportion of strains resistant to ampicillin, ampicillin / sulbactam and cefditoren pivoxil were noted for some years in comparison to the first year studied. There were no significant changes in the susceptibility to levofloxacin and clarithromycin. The proportion of strains resistant to ampicillin and cefditoren pivoxil showed statistically significant increases during the study period. The proportion of the strains resistant to ampicillin / sulbactam isolated from children was greater than from adults for every year studied. Levofloxacin resistant strains were isolated only from adults. The proportion of strains resistant to clarithromycin were about 1% in Japanese national surveillance data, but the proportions in this study were over 9%.<br><b>Conclusion</b> : Over a ten-year period in central Tokyo, <i>Haemophilus influenzae</i> strains resistant to ampicillin and cefditoren pivoxil increased. Strains resistant to clarithromycin occurred at a higher rate than nationally.